Could the STAN number be repeteable and random?

Question

I'm developing a Connector with some bank, and we're using the ISO8583 protocol, right now, i'm setting the STAN(field 11) with some random number generated with a random generator but sometimes I have some number collisions, the question is, could I safely use this generator or do I need to make the STAN a sequential number?

Thanks in advance.

Answer 1

Usually STAN is the number increased for each request. Random STAN generation is not the best case for network messages sequences.

The duplication of STANs can be due to different sources, i.e. Host clients or Terminals.

STAN itself cannot be the only field to detect unique transaction requests. It must be mixed together with other fields like RRN, Terminal ID, Merchant ID.

See also "In ISO message, what's the use of stan and rrn ?"

Answer 2

The System Trace Audit Number (STAN) ISO-8583 number has different values and is maintained basically between relationships within the transaction. That is it can stay the same or the same transaction will have many STANs over its transaction path but it SHOULD be the same between two end point and it is usually controlled in settings whos STAN to use.

For Example:

Terminal -> Terminal Driver -> Switch 1->Switch 2->Issuer

The STAN is say assign by the terminal driver and then remains constant at minimum for the following relationships... though may change for each relationship.

• Terminal Driver - Switch 1
• Switch 1 -> Switch 2
• Switch 2 -> Issuer

Note that internally within each system to the STAN may be unique as well but it needs to keep a unique STAN for each relationship.. and it shouldn't change between the request and response as it is needed for multi-part transactions (Single PA, Multiple Completions & Multi-PA, Single Completion) as well as for reversals and such in Data Element 90.

Answer 3

Depends on your remote endpoint, but I've seen many requiring sequential numbers, and detecting duplicates.